GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Oct 2018, 19:56

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# In the figure above, two security lights, L1 and L2 , are located 100

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 49968
In the figure above, two security lights, L1 and L2 , are located 100  [#permalink]

### Show Tags

18 Feb 2018, 23:02
00:00

Difficulty:

55% (hard)

Question Stats:

46% (02:46) correct 54% (02:31) wrong based on 69 sessions

### HideShow timer Statistics

In the figure above, two security lights, L1 and L2 , are located 100 feet apart. Each illuminates an area of radius 100 feet, and both are located 60 feet from a chain-link fence. What is the total length s of fence, in feet, illuminated by the two lights?

(A) 260

(B) 240

(C) 220

(D) 200

(E) 180

Attachment:

2018-02-19_1000.png [ 15.9 KiB | Viewed 826 times ]

_________________
BSchool Forum Moderator
Joined: 07 Jan 2016
Posts: 760
Location: India
Schools: ISB '20 (II)
GMAT 1: 710 Q49 V36
In the figure above, two security lights, L1 and L2 , are located 100  [#permalink]

### Show Tags

19 Feb 2018, 00:35
Bunuel wrote:

In the figure above, two security lights, L1 and L2 , are located 100 feet apart. Each illuminates an area of radius 100 feet, and both are located 60 feet from a chain-link fence. What is the total length s of fence, in feet, illuminated by the two lights?

(A) 260

(B) 240

(C) 220

(D) 200

(E) 180

Attachment:
2018-02-19_1000.png

100 . 80 . 60 triangle is formed wth the radius, fence and distance between fence n light source

three such triangles i.e length = 80+80+80 = 240

but some length isnt convered by three triangles thus >240

(a) imo
Intern
Joined: 15 Apr 2017
Posts: 1
Re: In the figure above, two security lights, L1 and L2 , are located 100  [#permalink]

### Show Tags

19 Feb 2018, 01:47

The lights make a 90 degree angle with the fence and hence the vertical distance is 60 feet. The lights cover 100 feet of radius , which means the triangle made is a pythagorus one with 100, 60 and uknown variable (calculate it to get 80). Thus, the light L1 covers a distance of 2(80) on fence and the L2 covers a little more than 80, making a total of more than 240.
Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3182
Location: India
GPA: 3.12
Re: In the figure above, two security lights, L1 and L2 , are located 100  [#permalink]

### Show Tags

19 Feb 2018, 10:22
2
Attachment:

2018-02-19_1000.png [ 16.62 KiB | Viewed 631 times ]

The centers of both the circles are at a distance of 60 feet from the fence.

Since the maximum distance that the light will travel is 100 feet,
using the Pythagoras theorem the vertical distance can be calculated as $$\sqrt{100^2 - 60^2} = \sqrt{6400} = 80$$

But the small distance(marked in red) in the figure is not yet accounted for.
The total length(s) of the fence which is illuminated by the lights is a little over 240.

Therefore, Option A(260) is the only option available(> 240) and is our answer.
_________________

You've got what it takes, but it will take everything you've got

Intern
Joined: 04 Jan 2018
Posts: 6
Location: India
Concentration: General Management, Operations
GPA: 3.72
WE: Operations (Manufacturing)
Re: In the figure above, two security lights, L1 and L2 , are located 100  [#permalink]

### Show Tags

20 Apr 2018, 05:35
The distance from L1 to L2 is 100.
If we drop a perpendicular from L1 to the fence at P and from L2 to the fence at Q, then the distance between P & Q will be 100. (L1 L2 Q P will be a rectangle)
100 . 80 . 60 triangle is formed with the radius, fence and distance between fence & light source.
So total distance = 80+100+80 = 260
_________________

-----
“A mind needs books like a sword needs a whetstone” - Tyrion Lannister

Re: In the figure above, two security lights, L1 and L2 , are located 100 &nbs [#permalink] 20 Apr 2018, 05:35
Display posts from previous: Sort by